An example of related art of a mobile communication system accommodating different types of access networks is recited in Non-Patent Literature 1.
As shown in FIG. 10, the mobile communication system recited in Non-Patent Literature 1 comprises a mobile network 1 and a mobile terminal 150.
The mobile network 1 comprises an HA (Home Agent) 120, an AAA (Authentication, Authorization and Accounting) server 121, an LTE (Long Term Evolution) network 111 and a WiMAX (Worldwide Interoperability for Microwave Access) network 112.
The LTE network 111, which is an access network for next-generation cellular radio communication for 3GPP called 4G, comprises a Serving GW (Gateway) 131, an MME (Mobility Management Entity) 132 and an ENB (Evolved-UTRAN Node B) 133. The Serving GW 131 is an anchor node for packet communication in the LTE network 111. The MME 132 is a control server for control signal processing in the LTE network 111. The ENB 133 is a base station for LTE.
The WiMAX network 112, which is an access network to which a radio technique defined by IEEE802.16e that is called 4G is applied, comprises an ASN-GW (Access Service Network Gateway) 141 and a BS (Base Station) 142. The ASN-GW 141 is a control server for control signal processing in the WiMAX network 112 and also an anchor node for packet communication. The BS 142 is a base station for WiMAX.
The HA 120 is an anchor node for continuously executing packet communication even when the mobile terminal 150 executes handover between different types of access networks such as handover (HO) from the LTE network 111 to the WiMAX network 112.
The AAA server 121 is a server for executing authentication and charging of the mobile terminal 150.
The mobile terminal 150, which is a terminal having performance of connection to both of the LTE network 111 and the WiMAX network 112, executes communication by using an IP address belonging to the HA 120.
In handover between different types of access networks in thus structured mobile communication system, operation will be as shown in FIG. 11.
As an initial state, the mobile terminal 150 is assumed to communicate through the LTE network 111.
When determining to execute handover from the LTE network 111 to the WiMAX network 112 because of a change of a radio condition or the like, the mobile terminal 150 first establishes a link with the BS 142.
Subsequently, the mobile terminal 150 sequentially executes access authentication, set-up of a radio bearer and IP address acquisition processing.
Since mobility management between the HA 120 and the ASN-GW 141 is executed by a mobility protocol called Proxy Mobile IP, the ASN-GW 141 registers a position at the HA 120 in linkage with the above-described IP address acquisition processing.
As a result of updating of position information of the mobile terminal 150 which is managed by the HA 120 by this position registration, handover to the WiMAX network 112 is completed.
Lastly, the mobile terminal 150 executes detachment processing with respect to the LTE network 111 not to be used.
Non-Patent Literature 1: 3GPPTS23.402 ver. 1.2.1 “3GPP System Architecture Evolution (SAE): Architecture Enhancements for Non-3GPP Accesses”, http://www.3gpp.org/ftp/Specs/html-info/23402.htm.
First problem is that time required for handover processing is long.
The reason is that attachment processing is executed as processing of handover (HO) between different types of access networks. Therefore, not only link establishment but also other lot of processing such as authentication processing and IP acquisition processing is required to result in having a longer handover time.